Queuing: The British take queuing very seriously. Always join the back of the line and wait your turn.
Personal space: Maintain a comfortable distance when talking. British people value personal space.
Greetings: A smile and "hello" or "good morning" is standard. Handshakes for formal meetings. Avoid hugging strangers.
Please and thank you: Use these constantly — it's essential to British politeness.
Indoor voice: Keep voices moderate in public spaces, especially on public transport.